JPH0862959A - Developer circulating/stirring device - Google Patents

Abstract

PURPOSE: To enhance the distributing efficiency of an elliptic blade and the stirring property of a developer and to prevent the density gradient and fogging of an image surface by smoothly taking the developer in a bucket roller without retaining the developer around the bucket roller. CONSTITUTION: In this developer circulating/stirring device provided with the bucket roller 12 in a main stirring part 11 and a spiral roll in a substirring part 21 and constituted so that the developer is carried from both end sides of the substirring part 21 to the central part, to be supplied to the main stirring part 11 and alternately distributed in opposite directions based on the rotation of the elliptic blade 16 inclinedly fixed on a rotary shaft 13 in the center of the bucket roller 12, to be carried to both end sides of the main stirring part 11 by the carrying work of supplying blades 19a and 19b and supplied to both end sides of the substirring part 21, that is, the developer is circulated in the shape of the figure 8 between the main and sub scanning parts 11 and 21, the length in the short radial direction of the elliptic blade 16 is made shorter than the outside diameter of the bucket roller 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer circulating and stirring device for circulating and transporting a powder developer while mixing and stirring the powder developer in a developing device such as a copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, as a circulation agitator for a developer composed of two components of toner and carrier, which is used in a developing device such as a copying machine or a printer, the first and second conveying paths, which are adjacent to each other in parallel, are provided at both ends. A first transport member that communicates through the passages in the central portion and moves the developer to these transport paths from both ends to the central portion; and a developer that is arranged in parallel with the first transport member to push the developer from the central portion to both end sides. Japanese Patent Laid-Open Publication No. HEI-3 (1998) -31868, which includes a second transport member that moves the developer, and circulates and transports the developer in an "8" shape between the two transport paths based on the rotation of these transport members. -260678.

Specifically, the first conveying member is provided with spiral blades whose spiral directions are reversed on both sides of a feeding member provided in the central portion as a boundary, and based on the rotation of the first conveying member. By the conveying action of the spiral blade,
The developer is conveyed from both ends of the first conveyance path to the center. Further, the second conveying member has a pair of side plates at both ends, a bucket having a substantially U-shaped cross section extending laterally at predetermined intervals on the outer periphery of the side plates, and a center of rotation of the second conveying member. And an elliptical blade attached at a predetermined inclination with respect to the rotation axis, and a plurality of blades are fixed to the inner surface of the bucket at predetermined intervals, and the mounting angles with respect to the bucket are set to be opposite with the elliptical blade as a boundary. It is composed of a feed blade, and the developer is conveyed while being agitated from the center of the second conveyance path to both ends by the conveyance action of the feed blade based on the rotation of the second conveyance member.

Based on the rotation of the elliptical blade, the developer supplied to the center of the second conveying path is alternately distributed to the left and right regions of the elliptical blade. Therefore, the developer that has been transported to the center from both ends of the first transport path based on the rotation of the first transport member and has been sent to the center of the second transport path by the above-mentioned feed member via the above-mentioned passage is distributed by the elliptical blades. By the action, they are alternately distributed to the left and right regions, and are transported to both end sides of the second transport path by the transport action of the feed blades provided inside the second transport member. That is, half of the developer conveyed from the left side area of the first conveyance path is conveyed to the right side area of the second conveyance path, and the remaining half is conveyed to the left side area of the second conveyance path. The same applies to the developer transported from the right side region of the first transport path. The developer transported to both ends of the second transport path is scooped by the bucket based on the rotation of the second transport member, and is sent to both end sides of the first transport path via the paths communicating with the first transport path. .

As described above, the developer in the left and right regions is mixed appropriately by circulating the developer in the shape of a figure between the first and second transport paths, and when the toner is replenished, the entire Therefore, there is an advantage that the toner density becomes uniform and the density gradient of the developing screen is prevented.

[0006]

However, in the developer circulating and stirring apparatus described above, the developer scooped at both ends of the elliptical blade facing the central passage communicating with the first conveying passage in the minor axis direction is elliptical. Since the force F that pushes outwardly of the second conveying member is applied by the rotation of the blades, the developer is not smoothly taken into the inside of the second conveying member and the second conveying member and the wall surface of the second conveying path are separated from each other. Retention of the developer occurred between the two. Therefore, the retained developer is pushed by the space between the second conveying member and the second conveying path without being distributed by the elliptical blades, and moves along the surface of the second conveying member to both end sides. To do. At this time, the developer conveyed from the left side area of the first conveyance path is in the left side area of the second conveyance path, while the developer conveyed from the right side area of the first conveyance path is in the right side area of the second conveyance path. It is in a so-called "one-sided circulation" state in which it is transported to the.

When a large number of original images each having a solid image consuming a large amount of toner on one side or a part of the original image are continuously copied in the state where the one-side circulation occurs as described above, even if toner is replenished, the image is developed. There is a problem that the image density differs between the left and right regions because the toner density does not become uniform quickly in the entire agent circulation agitator. Further, if the developer immediately after replenishment of the toner stays inside the second conveying member without being taken in, the amount of electrostatic charge of the toner will be insufficient due to insufficient stirring, so that the toner will scatter and cause fogging on the image surface. There was also.

By the way, it has been found that the distribution efficiency of the elliptical blade changes depending on the mounting angle of the elliptical blade and the rotation speed of the second carrying member. The mounting angle is most efficient in the vicinity of 60 ° with respect to the rotation axis, and the rotation speed of the second conveying member has a great influence on the developer supply amount to the adjacent developing magnet rolls, and therefore can be changed. Is limited.

Therefore, as a result of studying the shape of the elliptical blade in order to solve the above problems and further improve the distribution efficiency of the elliptical blade, the inventor of the present application conventionally has the same outer diameter as the second conveying member. By reducing the length of the elliptical blade in the minor axis direction, or by bending both ends of the elliptical blade in the minor axis direction in the rotational direction, it is possible to suppress the influence of the force F that causes the developer to stay. It has been found that the above problems can be solved.

[0010]

SUMMARY OF THE INVENTION The present invention has been made based on the above findings, and two agitating / conveying members are respectively provided in two developer conveying paths, and one developer conveying member is conveyed based on the rotation of these agitating / conveying members. In the path, the developer is conveyed from both ends to the central portion, and the developer fed from the central portion to the central portion of the other adjacent developer conveying path is transferred to the center of the stirring conveying member provided in this developer conveying path. Between the two developer transport paths by distributing them to the left and right by an elliptical blade attached obliquely to the rotation axis on the above-mentioned part and transporting them to both end sides of this transport path. In a developer circulating and stirring apparatus in which the developer is circulated and conveyed in the shape of a figure 8, the length of the elliptical blade provided in the central portion of the stirring and conveying member in the minor axis direction is set to be smaller than the outer diameter of the stirring and conveying member. It is a shortened one.

[0011]

In the developer circulating agitator having the above-mentioned structure, the elliptical blades are provided at both ends in the minor axis direction in comparison with the conventional case in which the length in the minor axis direction is equal to the outer diameter of the second conveying member. The force F for pushing out the scooped developer to the outside of the second transport member becomes weak. As a result, the developer is smoothly taken into the inside of the second transport member without staying, the distribution efficiency of the elliptical blades is improved, and the stirring property of the developer is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A developer circulating and stirring apparatus according to an embodiment of the present invention will be described below with reference to the accompanying drawings together with a developing apparatus equipped with this apparatus. FIG. 1 shows the overall structure of the developing device, which is roughly composed of a developer circulating and stirring device 1, a developing section 4, and a toner replenishing section 5.

The developer circulating stirring device 1 comprises a main stirring portion 11
And a sub-stirring section 21 provided at a position higher than the rear side (on the right side in the figure). The main stirring section 11 is provided with a bucket roller 12. The bucket roller 12 has side plates 14 and 14 (one of which is not shown) attached to both ends of a rotary shaft 13 connected to a drive system, and a bucket 15 is horizontally extended at predetermined intervals on the outer periphery of the side plates 14 and 14. The elliptical blade 16 is obliquely fixed to the rotary shaft 13 at the center. As shown in FIG. 2, the elliptical blade 16 has a hole 17 for inserting and fixing the rotary shaft 13 in the center of the elliptical plate, and has a shorter diameter than the conventional elliptical blade shown by a dotted line in the figure. And the length in the major axis direction is shortened.

A plurality of opposed feed blades 19 are attached to the inner surface of the bucket 15 at predetermined intervals, and as shown in FIG. The mounting angles are set oppositely. As a result, when the bucket roller 12 rotates in the direction of the arrow a, the feed blade 19a in the left side area of the elliptical blade 16 has a conveying action to the left side (direction of the arrow m), and the feed blade 19a in the right side area of the elliptical blade 16. 19b has a rightward (arrow n direction) conveying action.

Between the main stirring section 11 and the sub stirring section 21,
The partition walls 22a and 22b are provided symmetrically, and a passage 23 is formed between them as shown in FIG.
Passages 23a and 23b are formed outside the 2a and 22b, respectively, and the main stirring unit 11 and the sub-stirring unit 21 are connected to each other through these passages 23, 23a and 23b.

The sub-stirring section 21 has a spiral roll 24.
A sheet-shaped feed member 25 is provided at the center of the spiral roll 24. As shown in FIG. 3, spiral blades 26a and 26b whose spiral directions are opposite to each other are attached to both sides of the feeding member 25, and the developer is sub-stirred by the rotation of the spiral roll 24 in the direction of arrow b. Direction from both ends of 21 to the center (arrow m ',
It is transported in the n'direction). Further, a toner concentration detection sensor 27 is disposed on the bottom of the sub stirring unit 21 with its sensor surface facing the feeding member 25.

In the developing section 4, a first developing magnet roll 41 and a second developing magnet roll 42, which are opposed to the photoconductor 100 with a predetermined gap, are arranged side by side.
A first development region P ₁ and a second development region P ₂ are formed between the first and second development regions P ₁ and P ₂ , respectively. Behind the first developing magnet roll 41, a supply magnet roll 43 facing the bucket roller 12 is provided. These magnet rolls 4
Reference numerals 1, 42 and 43 are each composed of a fixed magnet body and sleeves that are provided around the fixed magnet body and are rotationally driven in the directions of arrows d, e and f, respectively. Further, a plurality of magnetic poles extending in the axial direction are arranged on the outer peripheral portion of these fixed magnet bodies, and non-magnetic pole portions M ₁ , M ₂ and M ₃ are formed in which magnetic poles of the same polarity are arranged. Further, between the second developing magnet roll 42 and the replenishing magnet roll 43, from this portion, the developing unit 4
A partition wall 44 is provided to prevent the developer from entering.

The toner replenishing section 5 is provided with a wall 51 located above the sub-stirring section 21 separated. The inside of the toner replenishing section 5 has partition walls 52 and 53 in which passages are formed.
The toner supply roll 57, the stirring blade 58, and the toner replenishment roll 59 are partitioned into the storage section 54, the stirring section 55, and the replenishment section 56 by the respective compartments, and are driven to rotate in the directions of arrows g, h, and i, respectively. It is provided. Based on the rotation of the toner supply roll 59, the toner is dropped and supplied to the main stirring section 11.

Next, the operation of the developing device having the above construction will be described. The developer consisting of toner and carrier is used as the main stirring unit 11 and the sub stirring unit 2 of the developer circulating stirring unit 1.
The toner is stored in the storage unit 54 of the toner supply unit 5.

In the sub-stirring section 21, the spiral roll 24
Due to the rotation of the developer, the developer is rotated by the spiral blades 26a, 26b.
Is conveyed from both end sides to the central portion by the conveying action. The developer, which has been conveyed from the left and right regions in the vicinity of the feed member 25 and merged, is fed into the main stirring unit 11 via the passage 23 by the rotation of the feed member 25. Further, the weight mixing ratio of the toner to the carrier of the developer merged at the central portion (hereinafter, referred to as “toner concentration”) is the toner concentration detection sensor 2.
If the toner density of the developer is equal to or lower than a predetermined reference value, the toner is replenished from the toner replenishing section 5 to the developer.

In the main stirring section 11, as the bucket roller 12 rotates in the direction of arrow a, as shown in FIG. 3, the developer sent from the sub stirring section 21 is alternately distributed right and left by the elliptical blade 16. To be The length 2r of the elliptical blade 16 in the minor axis direction is equal to the outer diameter of the bucket roller 12, as shown in FIG.
Since the length is shorter than R, the force F for pushing the developer scooped out on both ends 16a, 16b in the minor axis direction of the elliptical blade 16 facing the passage 23 to the outside of the bucket roller 12 is It becomes weaker than the conventional elliptical blade (see FIGS. 4 and 5).

Therefore, the developer is smoothly pushed into the inside of the bucket roller 12 without being pushed out to the outside and staying therein, and the distribution efficiency of the elliptical blades 16 is improved. As a result, half of the developer transported from the left side area of the sub stirring section 21 is more reliably transported to the right side area of the main stirring section 11, and the remaining half is more reliably transported to the left side area of the main stirring section 11. The same applies to the developer conveyed from the right side area of the sub stirring unit 21.

The developer distributed to the left and right regions of the main agitating section 11 is conveyed while being agitated to both end sides by the feed blades 19 of the bucket roller 12. Further, based on the rotation of the bucket 15, the developer is lifted rearward along the bottom surface and sent to the sub-stirring section 21 via the passages 23a and 23b, respectively, and then continuously conveyed in the direction of the arrow a to supply magnetic rolls. 43.

As described above, the efficiency of distribution of the elliptical blades 16 is improved, and the developer is more reliably distributed between the main stirring section 11 and the sub stirring section 21 while the stirring is sufficiently performed by the rotation of the bucket roller 12. By circulating and conveying in a character shape, it is possible to prevent the image density gradient caused by the one-sided circulation and the fogging of the image surface due to insufficient stirring of the developer.

The developer scooped by the bucket 15 and supplied to the replenishing magnet roll 43 is held on the sleeve around the outer periphery of the replenishing magnet roll 43 by the magnetic force. The developer conveyed according to the rotation of the sleeve in the direction of the arrow f is fed to the first developing magnet roll 4 before the non-magnetic pole portion M _3.
1 is supplied to the first developing magnet roll 4 by magnetic force.
1 Holds on the outer sleeve. The developer conveyed to the developing area P ₁ according to the rotation in the direction of the sleeve arrow d contacts the photoconductor 100, and develops the electrostatic latent image formed on the outer peripheral surface of the photoconductor 100.

The developer that has passed through the developing area P ₁ is
Subsequently, it is conveyed in the direction of the arrow d and is supplied to the second developing magnet roll 42 before the non-magnetic portion M ₁ . While being held by the magnetic force on the sleeve around the outer circumference of the second developing magnet roll 42, it is conveyed in the direction of arrow e as the sleeve rotates, and contacts the photoconductor 100 at the developing area P ₂ facing the photoconductor 100. The electrostatic latent image formed on the outer peripheral surface of the is redeveloped. Then, the developer that has passed through the second developing region P ₂ is continuously conveyed in the direction of the arrow e, and is separated from the second developing magnet roll 42 before the partition wall 44 facing the non-magnetic portion M ₂ , and the main stirring unit 11 Will be collected.

In the toner replenishing section 5, when the toner concentration of the developer detected by the toner concentration detecting sensor 27 is less than the reference value, it is supplied to the stirring section 55 based on the rotation of the toner supply roll 57 and stirred by the stirring blade 58. The toner is dropped and supplied to the main stirring unit 11 by the rotation of the toner supply roll 59.

As described above, in this embodiment, the elliptical blade 16
The length in the direction of the minor axis is smaller than the outer diameter of the bucket roller 12. Next, the dimensional conditions of the elliptical blade 16 obtained experimentally will be described with reference to FIGS. 6 and 7. .

First, as shown in FIG. 6, the length r from the center of the rotating shaft 13 to the outer peripheral edge of the elliptical blade 16 in the minor axis direction (hereinafter, referred to as “elliptic blade radius r”) of the bucket roller 12. FIG. 7 shows the radius R and the depth D of the developer pool in the main agitating section 11 with respect to the radius r of the elliptical blade obtained experimentally.
It is a graph showing the relationship among (1) density gradient, (2) fog density, and (3) developer distribution efficiency. From this graph, the elliptical blade 1 in which almost no density gradient or fogging on the image is generated and the developer distribution efficiency can be favorably maintained.
It can be seen that the optimum value of the radius r of 6 is in the following range indicated by the diagonal lines on the graph.

[0030]

[Formula 1] R-0.3D ≥ r ≥ R-0.5D

The elliptical blade 16 in the developer circulating and stirring apparatus 1 of the present embodiment is a conventional elliptical blade having an outer diameter substantially matching the outer circumference of the bucket roller 12, as shown in FIG. 8 (1). On the other hand, the lengths in both the minor axis direction and the major axis direction were shortened. However, as shown in FIGS. 8 (2) to (4), the dimension and shape in the major axis direction are the same as those of the conventional elliptical blade radius.
The length in the minor axis direction may be shortened by cutting out both ends in the minor axis direction into a linear shape, a wedge shape, or an arc shape within a range in which r satisfies the above formula.

FIG. 9 and FIG. 10 show another embodiment of a developer circulating agitator 1 '. The elliptical blade 16 'in this developer circulating and stirring device 1'has the same size and shape as the conventional elliptical blade in the major axis direction, but is bent at substantially right angles in the rotational direction by a predetermined width at both ends in the minor axis direction. is there. Since the other configuration is the same as that of the developer circulating and stirring device 1, the description thereof will be omitted together with the configuration and operation of the developing device including this device 1 '.

By doing so, the developer fed into the main stirring portion 11 from the center of the sub stirring portion 21 and scooped on both end sides of the elliptical blade 16 'is rotated outside the bucket roller 12 by the rotation of the bucket roller 12. Even if the force F that pushes the developer toward one side is applied, the developer is smoothly held inside the bucket roller 12 because it is held by the bent portions 16'a and 16'b formed at both ends of the elliptical blade 16 '. Is taken into.
Therefore, the distribution efficiency of the elliptical blades 16 'is improved and the stirring property of the developer is improved, so that the density gradient and fog on the image surface can be prevented. Further, since the circulation efficiency of the developer is improved, the range in which the rotation speed of the bucket roller 12 can be set is widened.

[0034]

As is apparent from the above description, in the developer circulating agitator according to the present invention, the agitating / conveying member provided in the developer conveying path for conveying the developer from the central portion to both ends, An elliptical blade for alternately distributing the developer fed from the adjacent developer transport path to the left and right regions is provided, and the length of the elliptical blade in the minor axis direction is shorter than the outer diameter of the stirring and transporting member. .

Therefore, the developer is smoothly taken into the agitating / conveying member without being pushed out of the agitating / conveying member by the rotation of the elliptical blade accompanying the rotation and being retained therein. For this reason, the distribution efficiency of the elliptical blades is improved, and the developer is more reliably circulated and conveyed in the shape of a figure between the two conveyance paths. Therefore, the toner concentration after replenishing the toner is the developer circulation stirring device. Quick and uniform throughout. Therefore, even if an image that consumes a large amount of toner is continuously created on one side by the developing device, a stable image without density unevenness can be always obtained without causing a density gradient.

Further, the developer is smoothly taken into the agitating / conveying member, and the distribution efficiency of the elliptical blades is improved, so that the agitating property of the developer is enhanced. As a result, it is possible to reduce the fogging of the image surface, which is caused by the insufficient charge amount of the toner due to insufficient stirring.

[Brief description of drawings]

FIG. 1 is a sectional view of a developing device equipped with a developer circulating and stirring device.

FIG. 2 is a front view of an elliptical blade.

FIG. 3 is a plan view of a developer circulation stirring device.

FIG. 4 is a cross-sectional view of a developing device for showing a cross section of a conventional elliptical blade.

FIG. 5 is a cross-sectional view of the developing device for showing a cross section of an elliptical blade in the embodiment.

FIG. 6 is a diagram for explaining an elliptical blade radius r, a bucket roller radius R, and a depth D of the developer pool.

FIG. 7 is a graph showing an optimum range of an elliptical blade radius r experimentally obtained.

FIG. 8 is a diagram showing a modification of the elliptical blade in the embodiment.

FIG. 9 is a cross-sectional view of a developing device for showing a cross section of an elliptical blade according to another embodiment.

FIG. 10 is a schematic view of a bucket roller for showing the shape of an elliptical blade in another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Developer circulation stirring device, 4 ... Development part, 5 ... Toner supply part, 11 ... Main stirring part (developer conveying path), 12 ... Bucket roller (stirring conveying member), 16 ... Elliptical blade, 21 ... Sub stirring Department
(Developer transport path), 24 ... Spiral roll (stirring transport member)

Claims (1)

[Claims] 1. An agitating / conveying member is provided in each of the two developer conveying paths, and based on the rotation of these agitating / conveying members, one of the developer conveying paths conveys the developer from both end sides to a central portion to be adjacent to each other. Send it to the center of the other developer transport path,
In the other developer carrying path, the developer is distributed to the left and right by an elliptical blade attached obliquely to the center of the stirring and carrying member with respect to the rotation axis, and is carried to both ends of this carrying path to carry the one developer carrying path. In the developer circulating agitator which is fed to both ends of the elliptical blade so as to circulate and convey the developer in the shape of a figure between the two developer conveying paths. A developer circulating and stirring device characterized in that it is shorter than the outer diameter of the conveying member.